Current assessment of “case clustering” of lymphomas and leukemias

Abstract

Epidemiologic studies of clustering of cases of leukemia and lymphoma have been mainly conducted to investigate the possibility that these diseases might have an infectious etiology. Many of the reported clusters of cases are impossible to evaluate statistically but controlled studies of “space‐time” clustering involving patients with leukemia and Hodgkin's disease (HD) have not yielded convincingly positive findings. We might not expect to find such clustering of cases, however, if the period between “infection” and onset is long. Special study of childhood leukemia, assuming a possibly long latent period, did not produce evidence of case‐to‐case transmission. The studies of HD are conflicting. Strong evidence of clustering of cases in schools has been reported in one U. S. Study but a similar British study did not find this and further investigations are necessary to determine whether case‐to‐case transmission may take place. There is indirect evidence which suggests that HD might arise as a rare response to a common infection. In such circumstances case clustering of HD would not necessarily be expected to occur. Space‐time clustering of Burkitt's lymphoma, (BL) has been a distinctive feature of the epidemiology of this disease though it has not been seen in all areas where BL is endemic. In a recent study, cases involved in such clusters were, on the average, older than other patients and this lends support to the notion that the clustering is a real effect and does not represent an artifact of case ascertainment. The currently favored etiology for most cases of “African” BL is that the disease arises as a result of some kind of interaction between infection with the Epstein Barr virus and chronic severe malaria. If this is so it is likely that infection with malaria is the event which precipitates onset of BL rather than infection with EBV and the clustering of cases is likely to relate in some way to malarial infection rather than to infection with EBV. Copyright © 1978 American Cancer Society